What to watch: Two Republican incumbents — Reps. Diane Black and Marsha Blackburn — are running for higher office (governor and Senate).
Why it matters: Only five of the last nine GOP incumbents to run for another office have won their primaries — three were endorsed by President Trump.
If history repeats itself, that means Blackburn should win tonight and Black will not as she didn't receive the coveted presidential tweet-endorsement.
One more thing: There are five incumbents (4 GOP and 1 Dem) running for re-election who are facing multiple primary challengers. Watch for any upsets in those congressional races in the 1st, 3rd, 4th, 8th and 9th districts.